Method of making tool handles



1949- c. u. COBERLY, JR 2,460,874

METHOD OF MAKING TOOL HANDLES Filed July 21, 1944 [NVENTO 3y CLARE/w; C09 {/2 THE HEM Arrows 5K5 Patented Feb. 8, 1949 TtOFFICE METHOD OF MAKING Clarence J. Goberly, Jr., San Marino, Calif., as-

signor, by mesne assignments,,to Kobe, In c.;,. Huntington Park, Calif., a'corporation 'of California Application July 21, 1944, Serial no. 546,029

3 Claims. (01. iiis9) 1 My invention relates to the art of making plastic objects. It is particularly applicable to the making of tool handles of plastic material, and will be described in connection therewith, al-

though I do not desire to be limited to the preferred embodiment described hereinafter, as the invention has other applications, as will be understood by those skilled in the art.

Tool handles are commonly made of wood or metal with a conical bore into which the shank of the tool to be held is driven to secure the handle to the tool. Attempts inthe art to utilize plastic materials, such as Bakelite, cellulose acetate, or the like, in the manufacture of such tool handles have not been successful, because of the characteristics of such materials. As is well known, plastic materials may be selected for widely different characteristics. Thus, relatively. soft plastics are available, which have high re-' sistance to breakage through'fracture, but such materials have the tendency to"flow when exposed to prolonged pressure engagementwith metals. If such a plastic material is used for a tool handle for a tool having a metal shank to be inserted into the holder, continued use of the tool causes the shank to enlarge gradually the receiving opening in the holder, due to.flow of the plastic material under pressure exerted thereon by the shank, with the result that the shank becomes loose in the holder and they tend to separate. On the other hand, if a plastic ma- I terial is selected which is hard enough to' resist this tendency to flow, it is ordinarily quite brittle, and the tool shank cannot be driven into the handle without a high percentage of break-' age of handles made from such'a relatively hard plastic material. Thus, attempts to use plastic materials for tool handles into which the metal shank of a tool is to be driven have not been successful.

It is therefore a primary object of my invention to provide a tool handle of relatively hard plastic material into which the metal shank of a tool can be forcibly driven without breaking the handle, and so as to retain the shank in the handle under all normal conditions of use. I accomplish this by molding into the plastic material of the handle a coil of spring wire axially aligned with the tool receiving bore of the handle, so as to reinforce the handle against breakage in assembly. This coil of spring wire, I have discovered, must have substantially more than one complete turn thereof, and preferably should have more than two complete turns, embedded in the plastic material of the handle. I 7

I have also discovered that it is desirable in such a handle as described above to embed the coil of spring wire in the plastic material of the handle so thatthe inner face of the coil is substantially in the plane of the bore of the handle, so as to eifectively'grip the tool shank when it is driven into the bore, and this is another object of my invention. 1 v

In, attempting to mold an annular reinforcing element. into the Wall of a tubular tool handle formed of plastic material, I have experienced difficulty in holding the reinforcing element in the desired .positionduring the molding operation. I obviate this ,difiiculty by using a coil of spring wire, as described above, which is snugly placed on a mandrel before molding, the tension in the wire causing it to retain its desired position on the mandrel'during the molding operation, and this is a furtherobject of my invention. ;'I'his expedient also insures that the inner wall of the coil is in substantially the same plane as the bore of the handle, which is an. additional advantage of the invention.

Another reason why plastic materials are not widely usedin the manufacture of'tool'handles for precisionitools is that'it is difiicult and expensive with known processes to permanently print identification marks on such materials, to identify the tool or instrument retained by the handle. It is therefore another object of the invention to provide'a simple and economical method of permanently fixing identification marks, or in fact any printing, on a plastic material; I accomplish this by pressing a hot die into the surface of the material to form indentations of desired configuration, painting the whole surface with a suitable paint and so as tofill the indentations, and then removing the paint and the beads formed'by the hot die from the surface of the material, to leave only the indentations filled with the paint. Thismethod is extremely fast, cheap, and forms permanent identification marks which are plainly visible and do not readily wear off through use dueto the fact that they are below thesurface of. the material and are thus protected from abrasion and other wear. Other objects and advantages of my invention will appear from the following specification and fromthedrawing, which is for illustrative purposes only andin which: Fig. 1 is a longitudinal sectional view through" my complete tool holder.

'Figf2 is aperspective view of the coil wire used in the invention.

of spring:

Fig. 3 is a longitudinal view, partly in section, showing my tool handle with a tool shank therein.

Fig. 4 is a view illustrating the first step of the method of my invention.

Fig. 5 is an enlarged fragmentary cross-sectional view taken on the line 5+5 of Fig. 3'. t

Fig. 6 isa view illustrating the first step of the printing method of my invention.

Fig. '7 is a bottom view of a die used in my printing method. 9

Fig. 8 is a view illustrating the effect of the first step of my printing method. r

Fig. 9 is a view illustrating a further step of essbeing old and Well known in the art. Since over its small end 22 and onto the frusto-conical portion 23 thereof, being moved onto the mandrel until the turns of the coil are slightly expanded, as illustrated. The exact position of the coil H on the mandrel 2| is not critical, and this preliminary step may be readily and quickly carried' "out by unskilled workmen. The tool handle t0 isthen'molded around the mandrel 2! so as to embed the coil I! in the inner wall of the tool handle, as illustrated, the general molding procthe coil I1 is slid onto the mandrel to the positronm which it snugly engages the mandrel, the 7 spring action of the coil retains it in the desired position on the mandrel during the molding operation, and no difiiculty is experienced in 1 forming the" finished product as illustrated in handle it, of generally tubular construction, pro:

vided with a bore H composed of a cylindrical portion 12 and a frusto-coni'c'a'l portion I 3; the exterior- M of which is preferably hexagonalm form; aspartially shown in Fig. 5, to provide'a series of flat faces l5. Obviously, the tool handle l e -may be made of any desired shape without d'eparting' from the spirit of my invention; The

handle i'ihand adjacent one end- 'thereof,- is acoil' 'll preferably formed of spring wire} It'isessentialthat the coil l'lbe formed or more than Iii one complete turn of spring wire so astd provide acontinuous circular reinforcement 'fo'r more than one complete turn about the frusto-coni'cal portion l3 of the bore H, andI' prefer to utilise approximately two and one-half turns ofwi re in the coil I! to avoid any possibility of fractureof the tool handle ID. More turns may be'employed' in the coil ll, but are unnecessary and merely add to the expense of the construction. will be noted, the inner face It of the coil H leappmximatelyirr. the plane'of the frusto conical portion I 30f the bore l-, andthisis arrimpcrtant' feature of the invention. t l

As illustrated in Fig. 3, the frusto-conieazl end 19 of a meta1 tool shank 20 is driven into the frusto-conical portion I3 of the bereft so asto tightly engage therein. The innerface I8= of the coil I] engages the face of the metal tool shank 29. to prevent the tool shank from being. driven into the tool handle I9 far enough to fracture the toolhandle, which is preferably of relatively brittle-material toinsure against flow thereof, and the coil also acts as a reinforcement for theplastic material-of which the handle is made. Tool handles made and applied in the manner described form a secure and. relatively permanent connection with the metal shank of a tool, and there is'llttle tendency, even after prolonged use by careless workmen, for the tool handles to loosen and fall off the'tool shanks.

Itiscommon practice in the art tomold'tubu lar plastic objectsupon a mandrel, and I- prcpose to follow this general practice, the tool handle ill being molded on a mandrel 2|, as illustrated in Fig.4 and as is well known intheart. Before molding, however, my invention contemplates: that the coil ll: be placed on the mandrel 21 in the position illustratedin -Fig. 4 in which it snugly engages the mandrel. To 'accomplish this, the coil I! need onlybe slidsonto-the-mandrct letter Fig. 1 If the coil 1'! has been slid farther onto the mandrel 21 than is illustrated in Fig. 4, before molding, in the finished product, obviously, it will be nearer the end of the tool handle l0 than il lustifated in Fig. 1, but this does not affect the operation or function of the device. Thus, there isconsiderable leeway in fabrication as to the exect pcsition of the coil ll on the mandrel 2| for molding. Another advantage-of my method is thatbyusing a coil of springwire, the coil can readily be distorted into the frusto-conical shape desired; Although I prefer to use a coil of spring wire; such asthe coil IT, I do not desire to be limited thereto, as obviously functionally equivalent 'ccils' canbesubstituted therefor without departing'from the spirit of my invention.

Figs. 5 to 10, inclusive, illustrate the method bywl iicli I print identifying indicia on one of the faces 1 5 of the tool handle" i0. Such'indicia are, normally in the form of words and numerals, but for simplicity l have shown'in Fig. 7- a die 25 having raised portions 26' adapted to form the The die 25 is first heated to a tem-- perature which will cause the plastic material of which the tool handle i0 is formed to flow and is then pressed'onto the flat face l5 of the tool handle, as illustrated in Fig. 6, to form indentatiens' 2'! therein." When the die 25 contacts the plastic material forming the tool handle lit, the

material-flows to: permit entrance of thedie thereinto and forms small raised beads 28- around the die on the surface of thefiat face i=5. Fig. 8 illustrates the condition of the surface afterthe die 25ahas' been removed therefrom, showing the indentations 2? and the beads 28'. As shown-in Fig. 9, the flat surface i5 is them entirely covered with a paint, preferably of a color contrasting with thatof the material of the tool handle ill, to form apain-t layer 2e thereon, which also fills the in-- dentations: 2]. After the paint layer 25 has fully dried, the paint layer together with the beads 28- are removed in" any suitable manner, as by buffing, to leave the flat face IS in the condition shown in Fig. 10, in which the face i5 is again flat but has: indented therein the indentations 2! filled with paint, which makes the lines formed by the die clearly visible, By filling depressed lines with: paint, in this manner, the paint does not wear ofi through handling, and is relatively penmanent.

Altlriough have shown and described a preferred' embodiment of my invention, it will be understood that certain features, elements, and steps "thereof are-merely representative of others which may be substituted therefor, and conseqnently I donut intendto' be' limited to the exact disclosure, but desire to be afforded the full protection of the'following claims.

I claim as my invention: 1

1. A method of forming a plastic article, including the steps of: forcing a coil of spring wire axially on a tapered mandrel so as to cause said coil to expand radially at a point where the coil snugly and inherently engages the mandrel; and molding a wall of plastic material around said coil and said mandrel so as to form a relatively hard plastic element having a bore of substantially the same diameter as said mandrel and having said coil embedded therein with the ends of said coil spaced from the ends of said bore.

2. A method of forming a plastic article, including the steps of: forcing a coil of spring wire axially onto a frusto-conical mandrel to cause said coil to expand radially until the inner wall of all of the turns of the coil snugly engages the mandrel so as to inherently hold said coil in position on said mandrel; and molding a wall of plastic material around said coil and said mandrel so as to form a plastic element having a frusto-conical bore of substantially the same configuration as the external surface of the mandrel and having said coil embedded therein with the ends of said coil spaced from the ends of said bore.

3. A method of forming a device of the character described, including the steps of: axially forcing a coil of spring wire on a tapered mandrel to cause said coil to expand radially to a point where said coil snugly and inherently enhaving said coil embedded therein with the ends of said coil spaced from the ends of said bore; and axially sliding said plastic element from said mandrel.

- CLARENCE J. COBERLY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 425,357 Wendlinger Apr. 8, 1890 1,037,759 Haskins Sept. 3, 1912 1,207,397 Greengood Dec, 5, 1916 1,589,913 Wells June 22, 1926 1,606,680 Wisner Nov. 9, 1926 1,650,307 Temple Nov. 22, 1927 1,800,254 Holmes Apr. 14, 1931 1,830,141 Stone Nov. 3, 1931 1,919,816 Wiegand July 25, 1933 2,106,186 Mulholland Jan. 25, 1938 2,208,494 Broderson July 16, 1940 2,345,749 Hohwart Apr. 4, 1944 2,378,901

Amrhein et al June 26, 1945 

